Blue lateral and purity magnet structure

ABSTRACT

A plurality of lateral magnets and purity magnets for use in a magnetic correction device and a method for making the same. The purity magnet comprises a ring and the lateral magnets are stamped from what would normally be the scrap from the center of the ring.

United States Patent Erickson June 26, 1973 BLUE LATERAL AND PURITY MAGNET STRUCTURE [56] References Cited [75] Inventor: Lloyd A. Erickson, Niles, lll. UNITED TATES PATENTS 2,533,688 12/1950 Quam 335/212 X [73 1 Asslgnee' g wmks Chlcagc" 3,376,450 4/1968 Franklin 335/212 x [22] Filed: Oct. 21, 1971 Primary Examiner-Ge0rge Harris [21] AppL No 191 447 Attorney-Robert W. Beart Related U.S. Application Data 57 ABSTRACT [62] Division of Ser. No. 883,938, Dec. 10, 1969, Pat. No. A plurality of lateral magnets and purity magnets for use in a magnetic correction device and a method for making the same. The purity magnet comprises a ring [22] 335l2llibiiililijgz) and the lateral magnets are Stamped from what would E g 302 306 normally be the scrap from the center of the ring.

12 Claims, 7 Drawing Figures BLUE LATERAL AND PURITY MAGNET STRUCTURE This application is a division of Ser. No. 883,938 filed 12-10-69 and now U.S. Pat. No. 3,646,669.

This invention, which relates to the magnetic correction of beam positions in cathode ray tubes, and more particularly to a blue lateral and purity magnet assembly for color television tubes and a method of making components thereof, is an improvement over US. Pat. No. 3,332,046 issued to R. R. Melone. While certain details, not relevant to applicants improvement, are not furnished herein reference may be made to the above mentioned Melone patent. However, the invention herein disclosed and claimed comprises an operable entity in itself without reference to Melone.

As is known, color television picture tubes as manufactured today comprise discrete dots of phosphors of three different colors. Three electron beams are respectively utilized for exciting the-phosphors. Quite precise positioning of the electron beams is necessary for each beam to excite its corresponding phosphor dots. Extraneous magnetic fields and manufacturing variations of color picture tubes may produce misregistration of the beam trios with respect to the associated phosphor dot trios. Compensation is effected by bending the three beams with a magnetic field produced by a pair of purifying magnets. This magnetic field is perpendicular to the tube axis and can be adjusted in magnitude and direction to correct for misregistration between the beam trios and the phosphor dot trios. The correction required must be adjustable from zero up to the maximum correction specified for a given type of tube.

Such magnet assemblies or purifying magnets heretofore have been constructed, and comprise a pair of flat magnetic rings mounted in face-to-face relation about the neck of the picture tube and coaxial therewith. The rings are magnetically polarized with discrete poles at spaced positions about their circumferences. The rings are rotatable relative to one another to determine the composite pole position and intensity, and the rings are rotatable as a unit to determine the direction of correction.

A deflection yoke for the color picture tube is ,supposed to converge the blue with the red and green beams. As a practical matter, the deflection yoke or radial-converging assembly is not capable of producing complete convergence of the blue and the converged red and green beams. In accordance with the principles of this invention, it is proposed to provide a device which will cause the blue and the converged red and green beams to move horizontally toward each other until they converge at or near the mid-point of the initial separation. This lateral motion of the beams provides a fourth degree of freedom to supplement the three provided by the radial convergence assembly.

In accordance with the Melone invention, the correction for the horizontal separation is achieved by bending the three beams with the magnetic fields produced by a lateral-converging device. Because the lateral error may be in either direction, and of any magnitude up to the maximum specified for the tube, it must be possible to change the direction of the magnetic fields, and the magnitude thereof over a range sufficient to compensate for the maximum possible error in the tube.

The invention herein disclosed accomplishes the same thing as Melone except thatin the Melone device it was found that there was a large waste of material in the production of individual components of the Malone assembly. 1

Accordingly, it is an object of the present invention to provide an improved lateral-converging device.

It is a further object of the present invention to provide a device which is readily mounted on the neck of a color picture tube as a unit, and which is adjustable to produce a desired degree and direction of lateral convergence.

A more specific object of the present invention is to provide in combination a blue lateral and purity magnet assembly for color television picture tubes.

Yet another object of this invention is to provide a lateral-converging device for color television picture tubes employing a pair of relatively rotatable ring magnets, magnetized with arcuately spaced poles, and further including means for arcuately and synchronously rotating said magnets relative to one another to provide the desired degree and direction of correction.

A still further object of the present invention is to provide in combination a blue lateral and purity magnet assembly for color television picture tubes with little or no waste material generated.

Yet another object of the present invention is to provide a method of making a blue lateral and purity magnet assembly for color television picture tubes with little or no waste material generated.

Other and further objects and advantages of the present invention will be apparent from the following description when taken in connection with the accompanying drawings, wherein:

FIG. 1 is an exploded perspective view of the device;

FIG. 2 is an axial end view of one portion of the device as taken substantially along the line 2-2 in FIG.

FIG. 3 is an axial sectional view taken substantially along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary sectional view of FIG. 2 taken along line 4-4 of FIG. 2; 4

FIG. 5 is a front view of a lateral magnet segment of.

the assembly;

FIG. 6 is an axial sectional view taken along line 6-6 of FIG. 5; and,

FIG. 7 is a front view of a purity magnet illustrating the making of the lateral magnets from the center scrap thereof.

The assembly 24 which is constructed for mounting on a neck portion of a color television tube (not shown) includes a housing or base 26 best seen in FIG. 1. It will be appreciated that this housing should have no electrical or magnetic effect on the picture tube. Consequently, the housing is made of moulded plastic material, and polycarbonate is one preferred material. The housing comprises a central cylindrical drum or mounting portion 28, having cylindrical segment inward projections 30 thereon as a result of molding die requirements. These projections are spaced from the neck of the picture tube and each of the four thereof is provided with an axial rib 31 spaced from the picture tube neck, but spaced closely thereto, to prevent or limit skewing of the assembly, which is mounted in a centilever manner as will appear hereinafter.

The rearwardly extending portion of the cylinder or drum 28 provides a seat 32 of cylindrical nature with shoulders 34 at the front thereof in a common diametral plane. The top and bottom shoulders are provided by external longitudinal projections. The side shoulders are provided by arcuately relatively long radial extensions, while the top and bottom shoulders are provided by an arcuately relatively short radial extension.

The side projections 30 extend rearwardly slightly beyond the cylinder or drum 28, while the top and bottom projections 30 extend a substantial distance past the rear thereof. The top and bottom projections 30 are provided with symmetrical, opposite arcuately extending flanges or wings 36, each of whichis provided at its outer end with a pressure pad (not shown). The wings 36 are quite flexible, and must be deflected slightly outwardly radially upon assembly of the housing with the neck of the picture tube. The resilient restoring force of the wings is not sufficient to be relied upon permanently to hold the housing in position, and this is taken care of as will be brought out hereinafter.

The housing also is provided with a magnet-mounting cylinder or cylindrical magnet seat 39, which is of larger diameter than the cylindrical tube gripping portion 28, and which is eccentric relative thereto. The walls of the two cylindrical portions are in part conincident. At the bottom part of the housing, the two cylindrical portions are spaced apart.

At the rear of the magnet-mounting cylinder 39, positioning shoulders are provided at 44 by means of relatively long arcuately radial projections 46 on the sides, and arcuately relatively short projections 48 at top and bottom. The top projection 48 also provides a rear upper shoulder 34 previously referred to.

The magnet-mounting cylinder 39 also is provided with top shoulders or stops, and these are such as to require individual attention. There are two lower side projections or shoulders 50 equally spaced about a vertical diameter, and spaced somewhat over apart. Each of these projections or shoulders subtends an arc of about 45. There are also two upper projections or shoulders 52, likewise symmetrically disposed about a vertical diameter and spaced about 20 arcuately from one another. However, each of the projections or shoulders 52 subtends a substantially smaller arc, say on the order of 20 to It will be appreciated that the shoulders 50, 52 are disposed arcuately so as to coincide with the spaces between the rear shoulder projections46, 48 for molding purposes. However, the particular spacing of the front shoulders 50, 52 serves a functional purpose in the assembly now being described, as will be brought out further hereinafter.

In addition to the foregoing, the housing 26 comprises an upstanding bracket 54. This bracket includes a central leg 56 upstanding from the upper projection 48, and further includes a pair of diagonal outer legs 58 extending from adjacent the shoulders 34 up to a transverse web (not shown) integrally joined to a top horizontal shelf 62 having a substantially U-shaped notch 64 therein opening forwardly. The web provided on the back side thereof, and at the outer edges thereof with a pair of horizontally disposed notches (not shown).

The purity magnet assembly 66 comprises a pair of steel rings, namely a front ring 68 andv a back ring 70. The ring 68 is provided with two diametrically spaced radially extending tabs 72 which are deflected forwardly, and the back ring 70 is provided with two diametrically spaced radially extending tabs 74 which are deflected to the rear. When both tabs 72 and 74 are aligned in normal position, as shown in FIG. 1, the front ring 68 is polarized so that there is a north pole at the left side thereof as indicated in FIG. 1, while there is a south pole at the right side thereof, 180 opposite. Similarly, the back ring is polarized with the south pole at the left, and the north pole 180 opposite at the right. With the two rings mounted in face-to-face relation, the magnetic poles shunt or cancel one another and there is a minimum magnetic field strength across the interior of the rings. The two rings can be rotated together by means of the tabs 72 and 74 to set the direction of the magnetic field. On the other hand, the rings can be rotated relative to one another to vary the effective field strength, following which the two rings are rotated as a unit to determine the direction.

The purity magnet assembly 66, comprising the rings 68 and 70, is held in place by a purity magnet retainer 76 of molded plastic material, nylon being a preferred example. The retainer comprises a split ring 78 which preferably is continuous, but shich can be split for ease of installation. Four inwardly directed teeth 82 at the back plane of the ring in an arcuately spaced relation fit behind the wings 36 of the housing 26, with the ring 78 surrounding the rear portion of the cylindrical portion 28. The ring further is provided with biasing flanges 84 which are arcuately spaced from one another and which are arcuately aligned with portions of the teeth 82. The biasing flanges 84 are deflected forwardly from the ring 78 and are tapered in a radially outward direction, whereby resiliently to bear against the rear ring 70, thus to hold the two rings 68 and 70 resiliently against one another and against the shoulder 34. This holds the magnetic rings 68 and 70 in a desired position, but allows ready circumferential adjustment thereof. Rearwardly projecting hooks 85 are provided to interfit with a clamping ring hereinafter to be described.

As will be appreciated, the natural resilience of the purity magnet retainer 76 and the housing pads (not shown) allows the ring to be flexed outwardly sufficient for installation. It will be observed that the retainer 76 and the magneticrings 68 and 70 are coaxial with the cylinder 28 and with the neck of the picture tube.

While somewhat out of the logical order of progression as to the functional parts of the invention, it is desirable at the present time to consider the clamp 86 which is located at the rear of the assembly for holding it in position. This clamp, as may be seen in FIG. 1, comprises spaced arcuate sections 88, 90, and 92. Offset radially outwardly thereof are arcuate portions 94 at the top and 96 at the bottom, respectively, interconnecting the arcuate portion 88 with the arcuate portions and 92. Lateral ears or flanges 98 and 100, respectively, project radially out from the arcuate portions 90 and 92. Both ears are provided with apertures, and the car 100 is provided with a helical impression 102 about the aperture. The clamp is received with the arcuate portion 88, 90 and 92, bearing against the wings 36 directly opposite the pressure pads. A screw 104 extends down through the ear 98 with the head H06 of the screw bearing against the ear, and with the threaded shank of the screw received in the helical impression 102 of the ear 100. Thus, the clamp 86 forces the pressure pads in against the neck of the picture tube securely, but resiliently, to hold the assembly in position on the neck of the picture tube. It will be appreciated that the radially outwardly offset portions 94 and 96 not only provide for clearance of the rearward extensions of the projections 30, but also equalize pressure on the pressure pads and provide a necessary degree of resilience to prevent unyielding clamping of the pressure pads such as might otherwise inadvertently fracture the neck of the picture tube.

A lateral magnet assembly 106 is mounted on the cylindrical portion 39 of the housing 26. The lateral magnet assembly comprises a pair of like magnet carrier rings 108 and 110 mounted in mirror image relation. The carrier rings should have no effect electrically, and a suitable grade of plastic material is preferred. One satisfactory example is heat resistant A.B.S. plastic. Each ring comprises a web 112, 114 having at the upper portion thereof an axially directed flange 116, 118. The axially directed segmental flanges 116, 118 are terminated by radial flanges 120, 122 having gear teeth 124, 126 thereon facing axially back toward the plane of the respective web 112, 114. Each gear segment 124, 126 and supporting flanges subtends a total are of about 80.

Each ring 108, 110 further has at its inner circumference axially extending flanges 128, 130 extending in the same direction as the flange 116. Each ring has radially inward protuberances from this flange. In particular, the ring 108 has diametrically oppositely disposed protuberances 132 lying on a horizontal diameter, while the ring 110 has similar protuberances 134. The protuberances 132 and 134 are of relatively short arcuate extent, being on the order of a total are of In addition, there are top and bottom protuberances 136 and 138, respectively, on the ring '108 and 110, these protuberances being of greater arcuate extent, on the order of 60. The protuberances 132, 134, 136 and 138 act as retaining lugs of a bayonet nature, as will be brought out shortly hereinafter.

Each ring further has a radial stop in the nature of a lug 140, 142, each such lug being a short distance above a horizontal diameter, and located to provide a predetermined amount of rotation based upon function, for example 14 above in one specific example. Each lug also is of rather short arcuate extent, on the order of 5.

Furthermore, each ring has a cooperating stop 144, 146 comprising a radial extension 148, 150, and an axial projection 152, 154 thereon, extending in a direction of the corresponding gear teeth. Each stop 144, 146 also occupies about 6 of arc, and the stop 144 is spaced from the stop 140 on the order of 137, the stops 146 and 142 being similarly spaced.

Each ring 108, 110 is completed by a plurality of protruding ribs and bosses and magnets held by the ribs and bosses. A detailed discussion of this feature will follow, with reference to FIGS. 2-7.

The arcuate size and dimension of the lugs 132, 134, 136 and 138 is such relative'to the flanges 50, 52 on the magnet-mounting cylinder 39 that with the rings 108, 110 rotated 90 from the position shown in the drawings, the rings can he slipped axially onto the cylinder 39. The radially inner ends of the lugs 132, 134, 136 and 138 form a fairly tight, sliding fit on the surface of the cylinder 39.

An adjustment member 168 is provided for the lateral magnet assembly, comprising a pinion 170 of proper diameter to fit between the gear segments 124 and 126 in mesh with both thereof. The adjustment member including the pin is an integral plastic molding,

and nylon is one preferred example of a satisfactory plastic material. Immediately above the pinion 170 there is a restricted neck 172 having a boss (not shown) thereabove with a radially extending circumferential flange 176 above the boss. A knurled finger piece 178 extends upwardly from flange 176 for ready gripping by the fingers to rotate the pinion. In addition, a screw driver slot 179 is provided in the end of the finger piece 178 as an additional means of adjustment if so desired.

The adjustment member is received with the boss thereof in the U-shaped slot 64 of the shelf or platform 62 at the top of the bracket 54. The teeth of the pinion 170 mesh with the gear segment teeth 124, 126, as mentioned previously, and the flange 176, rests on top of the shelf 62. The finger piece 178 is relatively rotated in either direction by the thumb and first finger to adjust the positions of the magnet carriers 108, relative to one another. It will be apparent that the stops 144, 146 engage one another in one direction of rotation to limit rotation in that direction, while the stop 146 engages the stop 140, and the stop 144 engages the stop 142 in the other direction of rotation, thereby limiting the total rotation between the two rings and magnets to an extent that the pinion does not run off the gear segments at either end. It will be observed that the magnetic poles oppose and cancel each other with the rings in the position shown. In the present example with six pole magnets, the rings are each capable of 30 rotation in either direction, a relative rotation of 60, so that the magnetic poles can reinforce one another. The direction of relative rotation determines the direction (and magnitude) in which the resulting magnetic field will be oriented.

The adjustment member 168 is held in place by a retaining spring 180. The retaining spring is made of a suitable resilient gmetal. Phospor bronze being a satisfactory example. The retaining spring includes an elongated front face or web 182 which fits against the front or left edge of the shelf 62 of the bracket 54 as viewed in FIG. 1. A central depending finger 184 with a spherical impression 186 near the lower end thereof serves to support the ring gear sector and to insure positive engagement with pinion and to prevent ratcheting therewith. A protuberance (not shown) on the leg 58 bears on the adjacent ring, and this protuberance and the finger 184 compensate for plastic creep or flow at elevated temperatures. The spring retainer further includes a pair of flanges 188 extending rearwardly from the bottom edge of the web or face 182, and having intermediate fingers 190 extending therefrom beneath the shelf 62, and having a cammed extremity 192 to facilitate installation. A

The spring retainer further has a pair of side arms 194 extending to the right in FIG. 1 and having at the extremities thereof downwardly turned latching fingers 196 having offsets or detents 198 with outwardly directed end pieces 200. The detents are received in the notches 65 on the bracket 54, thus latching the spring retainer unit in place. The spring retainer can be removed by lifting up the latching fingers 196 and side arms 194 with a finger-nail below the outwardly turned tips 200 thereof.

The intermediate legs 190 fit in the restricted neck 172 of the adjustment member to hold the adjustment member in place. Furthermore, the intermediate legs 190 are bowed down so as to bear resiliently against the top edge of the pinion 170 thereby to hold the adjustment member firmly down in place with the flange 176 thereof bearing against the top surface of the shelf 62. This insures against loose fitting of mismatched or off tolerance parts, and provides a friction brake to avoid undesired angular movement of the magnet mounting rings 108, 110.

It will be appreciated that the adjustment member prevents movement to the rings to such a position that they can be axially withdrawn, and effectively provides a selflocking feature preventing rotational movement due to a unidirectional force tending to rotate both rings in the same direction, such as may occur during handling before or after installation on the picture tube.

Turning to FIGS. 2 to 4 in conjunction with FIG. 1 the magnet carrier ring 110 of the lateral magnet assembly 106 is shown with three protruding boss members, 300a, 300b and 3006 connected to and protruding from the web face 114 of the magnet carrier ring. The boss members are arranged on a common circle just within the outermost edge of the carrier ring having as its center, the center of the carrier ring and equally spaced apart. The magnetic carrier ring also has three pairs of right-angular shaped rib members 3021; and 302b, 304a and 304b, and 30611 and 306k positioned on the web face 114 and extending out therefrom. The rib members of each pair are positioned co-operatively a predetermined distance apart and below a corresponding boss as can be seen in FIGS. 1 and 2. Each boss and corresponding pair of rib members protrude a sufficient distance from the web face so that a lateral magnet as described hereinafter may be securely fastened thereto. The magnet carrier ring 108 also has three protruding boss members and three pairs of right-angular shaped rib members positioned thereon in the same manner discussed above, as seen in FIG. 1.

A lateral magnet 308a (FIGS. 5 and 6) representative of the lateral magnets discussed herein is crescent shaped, having a flat body 30% with an arcuate upper edge 3080, an arcuate lower edge 308d of greater diameter, two straight end edges 308e. Respective north and south poles are provided adjacent the end edges. The radius of curvature of the lower edge is equal to the radius of curvature of the inner edge 309 of magnet carrier rings 110. A bore 310 extends through body 308b at the top center of the magnet 308a and is sized for reception of protruding boss 300a.

The magnet is affixed to the magnet carrier ring 110 by placing the magnet flat on the web face 114 of ring 110 with the boss 300a inserted through the bore 309a of the magnet with the edges 3082 of the magnet set flat on the horizontal legs of rib members 302a and 302D respectively. With the magnet so positioned it can be seen from FIG. 2 that the lower edge 308d of the lateral magnet coincides with the inner edge 309 of the carrier ring. The magnet is thereafter permanently secured to the carrier ring by applying a hot tool such as a soldering iron to the boss, causing the end of the boss to mushroom beyond the bore as seen in FIG. 3. It is, of course, understood the magnet may be permanently secured to the carrier ring by using an adhesive material.

Two remaining magnets 308a are positioned on the ring 110 in the same manner as discussed above. It should be understood that the invention herein disclosed and claimed is not limited to the use of three magnets. A greater number as well as a smaller number of magnets may be affixed to the carrier ring. it also is to be understood that the manner of mounting the mag nets is not limited to that discussed above. The magnets for example may be recessed so as to be flush with the Carrier ring. As noted above, each magnet has a north pole at one end thereof and a south pole at the other end. The magnets are positioned on the ring so that a north pole of each of said magnets lies adjacent a south pole of an adjacent magnet.

Three lateral magnets similar to those discussed above are placed on the web face 1 12 of magnet carrier ring 108 in the same manner as the magnets 308a, 3118b and 3080 are placed on web face 114, as seen in FIG. 1. Thus the lateral magnets of carrier ring 110 and the lateral magnets of carrier ring 108 ride in face-to-face relationship with their poles relatively reversed with respect to each other.

With reference to the method of making the above described lateral magnets, attention is directed to FIG. 7 which shows a metallic disc 311 before the center cir cular portion 312 has been removed. Dashed lines 313a, 313k and 313a represent the contour of three lateral magnets as described above. The lateral magnets will be manufactured from this center portion by utilizing appropriate cutting and stamping tools and a purity magnet 68 or will be made from the remaining ring. The lateral magnets preferably are stamped out and formed simultaneously with the removal of the center circular surface of the disc, saving time in the manufacturing of the device herein disclosed. If a greater number of lateral magnets are desired they may be made from the purity magnet rings in the same manner as discussed above, but, of course, they will be smaller in size than those shown in the embodiment herein. The exact stamping and cutting processes in making the magnets are conventional and therefore will not be discussed herein.

The method of making the lateral magnets, as well as a purity magnet, is as follows: the disc 311 is formed from a metallic material which is suitable for carrying a permanent magnetic charge; the center circular portion 312 of the disc is removed leaving a ring portion 316; the metallic material within dashed lines 313a, 313b and 313C is cut from the material of the center portion and magnetized, as is ring portion 316, to inelude north and south poles. The ring portion 316 after magnetization can then be used as a purity magnet 68 or 70 and the material defined by dashed lines 313a, 3131; and 3130 after magnetization can be used as lat eral magnets as described above. It should be noted that the above steps preferably are contemporaneous.

It can be seen from FIG. 7 that there is very little waste material after the lateral magnets have been removed. Upon a detailed inspection of FIG. 7, it is observed that the upper areuate edge of each magnet has a radius of curvature equal to the radius of curvature of the inner circular edge 3141 of the purity magnet and the radius of curvature of the above mentioned upper arcuate edge is preferably the same but can be greater than the radius of curvature of each magnets lower arcuate edge. This design eliminates a major portion of waste as discussed above.

The structure of the invention has now been disclosed, and it will be apparent that the assembly fits readily on the neck of a color television picture tube, being held in place by the clamp or retaining ring 06. The purity magnets 68 and 70 are adjusted individually and together to produce the proper strength and direction to compensate for the earth magnetic field as well as other stray fields that might be present at any particular installation. These magnets, as has been noted heretofore, are concentric with the center line of the picture tube.

The lateral magnets and mounting or carrier rings are adjustable equally and oppositely about an axis which is eccentric relative to the axis of the picture tube. The direction of rotation determines the direction of magnetic correction about a zero or null point, and the degree of rotation determines the strength of the magnetic field, thereby effecting lateral convergence of the blue beam with the red and green electron gun beams. As will be appreciated, the corrections are made while observing the picture tube so that the direction and degree of adjustment can be made empirically.

The specific embodiment of the invention as herein shown and described will be understood as being for illustrative purposes only. Various changes in structure will no doubt occur to those skilled in the art, and will be understood as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.

The invention is claimed as follows:

1. A lateral magnet assembly for use in a magnetic correction device comprising: two non-magnetic carrier rings; boss means located on and protruding from each of said carrier rings; rib means located on each of said carrier rings; and at least one lateral magnet with magnetic north and south poles mounted on each of said carriers by said boss means and said rib means.

2. A lateral magnetic assembly according to claim 1 wherein said boss means include at least one protruding boss member for each lateral magnet to be mounted and said rib means includes at least one protruding rib member for each of said boss members.

3. A lateral magnetic assembly according to claim 2 wherein said rib means includes two protruding rib members for each of said boss members whereby each magnet is mounted on a surface of each carrier ring by one boss member and two rib members.

4. A lateral magnetic assembly according to claim 3 wherein, there are at least two magnets and each of said magnets includes a flat body portion with an upper arcuate edge, a lower arcuate edge, two edge means joining together said arcuate edges for mounting on a respective rib member, each of said edge means having a respective north and south pole, and a bore through the surface of said magnet for receipt of said boss memher.

5. A lateral magnet assembly according to claim 4 wherein each of said non-magnetic carrier rings has an inner circular edge having a radius of curvature substantially equal to the radius of curvature of each inner arcuate edge of said magnets.

6. A lateral magnet assembly according to claim 5 wherein said boss members are located on a common circle having as its center the center of said carrier ring and said magnets are mounted on said carrier rings such that the distance from the center to said inner circular edge is equal to the distance from the center to the lower arcuate edges of each magnet.

7. A lateral magnet assembly according to claim 6 wherein said boss members are equally spaced apart whereby said magnets are equally spaced apart.

8. A lateral magnet assembly according to claim 7 including three lateral magnets mounted adjacently on each of said carrier rings whereby a north pole of each of said magnets lies adjacent to south pole of an adjacent lateral magnet.

9. A lateral magnet assembly for use in a magnetic correction device comprising: two non-magnetic carrier rings; a plurality of lateral magnets, each with magnetic north and south pole means, mounted on a common surface of each of said carrier rings; and means mounting said magnets adjacently on said carriers whereby a north pole of each of said magnets is adjacent a south pole of an adjacent magnet, the magnets on the respective carriers being in substantially face-toface confronting relation.

10. A lateral magnet assembly according to claim 9 wherein each of said magnets includes an upper arcuate edge, a lower arcuate edge, and two end edge means joining together said arcuate edges each of said edge means having a respective north and south pole.

11. A lateral magnet for use in a magnetic correction device comprising: a thin body portion having an upper arcuate edge, a lower arcuate edge and two end edge means joining together said arcuate edges, the distance between said upper and lower arcuate edge being at least twice the thickness of said thin body portion each of said edges having a respective north and south pole: and means to mount said lateral magnet on said device.

12. A magnet according to claim 11 wherein said body portion mounting means includes a bore through said end edges are straight edges. 

1. A lateral magnet assembly for use in a magnetic correction device comprising: two non-magnetic carrier rings; boss means located on and protruding from each of said carrier rings; rib means located on each of said carrier rings; and at least one lateral magnet with magnetic north and south poles mounted on each of said carriers by said boss means and said rib means.
 2. A lateral magnetic assembly according to claim 1 wherein said boss means include at least one protruding boss member for each lateral magnet to be mounted and said rib means includes at least one protruding rib member for each of said boss members.
 3. A lateral magnetic assembly according to claim 2 wherein said rib means includes two protruding rib members for each of said boss members whereby each magnet is mounted on a surface of each carrier ring by one boss member and two rib members.
 4. A lateral magnetic assembly according to claim 3 wherein, there are at least two magnets and each of said magnets includes a flat body portion with an upper arcuate edge, a lower arcuate edge, two edge means joining together said arcuate edges for mounting on a respective rib member, each of said edge means having a respective north and south pole, and a bore through the surface of said magnet for receipt of said boss member.
 5. A lateral magnet assembly according to claim 4 wherein each of said non-magnetic carrier rings has an inner circular edge having a radius of curvature substantially equal to the radius of curvature of each inner arcuate edge of said magnets.
 6. A lateral magnet assembly according to claim 5 wherein said boss members are located on a common circle having as its center the center of said carrier ring and said magnets are mounted on said carrier rings such that the distance from the center to said inner circular edge iS equal to the distance from the center to the lower arcuate edges of each magnet.
 7. A lateral magnet assembly according to claim 6 wherein said boss members are equally spaced apart whereby said magnets are equally spaced apart.
 8. A lateral magnet assembly according to claim 7 including three lateral magnets mounted adjacently on each of said carrier rings whereby a north pole of each of said magnets lies adjacent to south pole of an adjacent lateral magnet.
 9. A lateral magnet assembly for use in a magnetic correction device comprising: two non-magnetic carrier rings; a plurality of lateral magnets, each with magnetic north and south pole means, mounted on a common surface of each of said carrier rings; and means mounting said magnets adjacently on said carriers whereby a north pole of each of said magnets is adjacent a south pole of an adjacent magnet, the magnets on the respective carriers being in substantially face-to-face confronting relation.
 10. A lateral magnet assembly according to claim 9 wherein each of said magnets includes an upper arcuate edge, a lower arcuate edge, and two end edge means joining together said arcuate edges each of said edge means having a respective north and south pole.
 11. A lateral magnet for use in a magnetic correction device comprising: a thin body portion having an upper arcuate edge, a lower arcuate edge and two end edge means joining together said arcuate edges, the distance between said upper and lower arcuate edge being at least twice the thickness of said thin body portion each of said edges having a respective north and south pole: and means to mount said lateral magnet on said device.
 12. A magnet according to claim 11 wherein said body portion mounting means includes a bore through said end edges are straight edges. 